Somewhat unthinkably, for the last two years the Library of Congress has archived the "Twittersphere," spooling every public tweet onto magnetic tape that's batched by the hour and filed away in cabinet drawers. With the Twittersphere's pulse running at about 700 million tweets per day, those miles of tape begin to look like one inscrutable cultural EKG. Nobody's quite sure what it all amounts to, though most of us feel, much of the time, that we're hyperventilating.

Things have been speeding up, steadily, for a long time. In the 19th century, thanks to the instantaneous information streams of the telegraph, we began to believe in something called "news of the day." Today the belief is something more like: it's all news, everywhere, always, with "news" understood to refer to Syria, the Super Bowl, Obama and "The Bachelor" alike. We seem to be at a point of ultimate feed density. Despite (or because of) the superabundance of "info," we're often purely confused. Amid our frantic upping of "updates," what can we actually know -- beyond what we constantly broadcast of ourselves -- about the people we collectively are, and are becoming?

In her debut essay collection, "This Is Running for Your Life," Michelle Orange models an ideal balance of firsthand engagement with -- and grounded criticism of -- the lightheaded culture all around us. "The new American dream," she writes, "is to build a really (cool) personal brand, and the result of all that tap dancing on all those individual platforms is a pervasive kind of narrative decadence. We race to consume and regurgitate the hour's large and small events for each other like patricians in a postmodern vomitorium -- to know them first, translate them into bitter capsule form fastest, and be shocked or stirred or perceived as in any way less than totally savvy about these things the least. Even within our self-contained realities we become dulled to what's real and what's not, and further desensitized to what lies behind our fellow performers' virtual scrims." Here and elsewhere in the book, Orange's insights share their probing, persuasive rhythms with those of Susan Sontag, whose name rightfully comes up a number of times.

In the stunning chapter "Pixelation Nation," which takes its cue from Sontag's hallmark 1977 book "On Photography," Orange explores the scarcely considered implications of digital imagery and dissemination in a time when every smartphone, iPad and iPod is a camera which, "with its promise of perfect recall, both reminds and relieves the shooter of the burden of being present." As we each become daily -- not to mention hourly -- publishers of images we've captured and edited for immediate upload, the images themselves take on "more of a social than a subjective or individual purpose." Our pictures have become part of a larger, ongoing self-publicizing project: "It's more about representing a certain reality than remembering it."

It's this kind of unfailingly X-ray-like inquiry into the peculiarities of our ultra-mediated world that unites Orange's 10 absorbing essays. Where Sontag's work generally took literature as the hub of its radial concerns, Orange proves herself an eloquent revealer of things more broadly socio-cultural and, as it happens, patently bizarre -- though they're the very things we refer to as "daily life. " She describes a generational scarcity of time, a constant low-level panic, status anxiety, pervasive irreality and indefinable alienation felt by anybody and everybody in these hyper-technologized days. Meanwhile, she is often winningly personal in her tone and disclosures: the final essay, exploring Orange's addiction to long-distance running, is a marvel of memoir, cultural critique and metaphor.

At heart, what worries Orange is the plight of the good old-fashioned vulnerable self, and "This Is Running for Your Life" is all about the importance of "constant searching, through a mustard-fog of rhetoric and reflexivity, for one's own response." Her own search, demonstrated here, deserves our admiration.